The major objective of the proposed research is to elucidate the mechanism of neuroendocrine control of reproductive function by investigation of the inhibitory effects of pineal indole compounds on the pituitary response to luteinizing hormone releasing hormone (LHRH). A highly enrichd population of gonadotroph cells will be utilized to study the intracellular mechanism of action of melatonin and serotonin in inhibiting luteinizing hormone and follicle stimulating hormone secretion. These studies will involve examination of the effects of melatonin and serotonin on the kinetics of LHRH-receptor interaction and changes in intracellular cAMP and cGMP. In addition, evaluation will be made of the developmental decrease in pituitary responsiveness to melatonin, in particular with regard to its potential role in regulating maturation of the reproductive system, and of the interaction between gonadal steroids and pineal indoles in regulating pituitary responsiveness to LHRH in the neonate and in the adult animal. Characterization of these hormonal interactions will provide a clearer understanding of the role of pineal gland in the control of reproductive function and will permit rational approaches to the pharmacological control of these neuroendocrine systems for purposes of fertility and developmental reproductive control.